A cogeneration system supplies generated electric power to users for electric power loads, and recovers and stores exhaust heat for hot water supply loads of the users, the exhaust heat being generated by the electric power generation. Known as this type of cogeneration system is a cogeneration system configured such that a fuel cell and a water heater operate by the same raw material (see PLT 1). The system of PLT 1 includes: a fuel cell; a heat exchanger configured to recover heat generated by the operation of the fuel cell; a hot water tank configured to store water having flowed through the heat exchanger to be heated; and a water heater configured to heat the water flowing out from the hot water tank up to a predetermined temperature. The system is configured such that the fuel cell and the water heater operate by the same raw material.
Moreover, a configuration is known, which is provided for the purpose of improving an exhaust performance of the fuel cell system provided inside a building (see PLT 2). In PLT 2, the fuel cell system provided and used inside the building including an intake port is disclosed. The system includes an air introducing port through which air inside the building is introduced to the inside of the fuel cell system, an air discharging pipe through which the air inside the fuel cell system is discharged to the outside of the building, and a ventilation unit. Air outside the building is introduced to the inside of the building through the intake port by the ventilation unit and to the inside of the fuel cell system through the air introducing port, and is discharged to the outside of the building through the air discharging pipe.
Further, a fuel cell system including a duct extending in a vertical direction is known, which is configured for the purpose of improving exhaust performance of an exhaust gas generated by the fuel cell system provided inside a building (see PLT 3). The duct provided in the fuel cell system of PLT 3 extends in the vertical direction inside the building and has an upper end portion located outside the building. Further, the duct has a double pipe structure having an inner passage and an outer passage, and a ventilating pipe and an exhaust pipe are coupled to the inner passage or the outer passage of the duct such that an exhaust gas or air independently flows through the inner passage and the outer passage of the duct.
Further, a fuel cell system that prevents water generated in a fuel cell from freezing is known (see PLT 4). In the fuel cell system of PLT 4, heat exchange occurs between exhaust gas from the fuel cell and intake air (external air) supplied to the fuel cell to heat the intake air and prevent the freezing.